In a conventional integrated circuit package, such as a conventional flip chip package, a plurality of conductive posts may be provided between top and bottom substrates or interposers. An integrated circuit die, for example, a flip chip die, may be attached to one of the substrates or interposers, for example, the bottom substrate or interposer, and positioned between the two substrates or interposers. A plurality of conductive posts are provided between the top and bottom substrates or interposers to provide mechanical support as well as electrical connections for the integrated circuit package. These conductive posts may be copper posts for good electrical conductivity. Each of the top and bottom substrates or interposers may include a plurality of conductive contacts, and the conductive posts may be coupled between some of the conductive contacts in the bottom substrate or interposer and some of the conductive contacts in the top substrate or interposer.
In a conventional process for making such an integrated circuit package, the conductive posts, such as copper posts, are provided directly on respective conductive contacts in one of the substrates or interposers, for example, the top substrate or interposer. A plurality of solder balls may be provided on respective conductive contacts in the other substrate or interposer, for example, the bottom substrate or interposer. The copper posts, which are attached to the respective conductive contacts in the top substrate or interposer, are soldered to respective conductive contacts in the bottom substrate or interposer with respective solder balls. After the top and bottom substrates or interposers with copper posts are assembled to form an integrated circuit package, which may sit on the bottom substrate or interposer, the only mechanical support for the top substrate or interposer may be provided by the copper posts.
In such a conventional integrated circuit package, the copper posts may have a tendency of cracking or breaking in the manufacturing of the top substrate or interposer to which the copper posts are attached. Such a tendency for cracking or breaking of copper posts may results in a low yield in the manufacturing of the copper post substrate, low yield in the assembly of copper post package and a high risk of reliability test failure, thereby increasing the cost of manufacturing. Various schemes have been devised in attempts to increase the manufacturing yield for the copper posts and to decrease the risk of reliability test failure. One such scheme is to provide a mold or epoxy flux that fills the entire interior space between the top and bottom substrates or interposers of the integrated circuit package to protect the copper posts. However, such a scheme may involve an expensive manufacturing process and still may not improve the yield for copper substrate manufacturing.